【作者】 赵玉集；

【导师】 刘大锰； 姚艳斌；

【作者基本信息】 中国地质大学(北京) ， 油气田开发工程， 2012， 博士

【摘要】 三江-穆棱河含煤层区煤层气资源量丰富，是中国低阶煤层气开发的前景区之一。但由于构造演化复杂、含煤层系沉积环境多变、煤层层数较多、煤层厚度较薄且不稳定，导致煤层气富集成藏及控制机理难以准确把握，为寻找煤层气勘探开发区增加了难度。本文以4个主要含煤盆地（鹤岗、鸡西、虎林和勃利）和1个拗陷（绥滨）为例，研究了含煤区地质条件、含煤层系沉积环境、煤储层发育特征以及煤层气富集规律，为煤层气资源评价及有利区优选提供依据。主要成果和认识如下：（1）研究区经历了多期构造升、降作用。在城子河组时期，勃利、鸡西盆地和绥滨拗陷均经历了较大强度的断陷作用，沉积了巨厚的含煤沉积建造。虎林盆地在古近纪再次拉张裂陷，发育了巨厚的含煤地层。在城子河组时期，绥滨拗陷主要为湖泊相沉积环境，有利聚煤带位于三角洲前缘和滨浅湖相；勃利盆地主要以河流和河控三角洲聚煤为主；鸡西盆地主体环境为三角洲平原和河流洪泛平原沉积，有利于成煤。古近系虎林组是虎林盆地主要含煤地层，其沉积环境为河流相和湖泊相。（2）采用压汞法、低温氮法、等温吸附测试、显微组分和显微裂隙统计分析等实验研究了含煤区煤储层物性特征。结果表明：①煤岩显微组分以镜质组为主（34.0-95.1%），其次为惰质组（0.6-62.7%）以及少量的壳质组（0.7-18.2%）。②煤岩以微小孔为主（平均55.9%），大孔和中孔含量中等（平均22.3%和21.8%）。其中，微孔比小孔含量高，两者比值为0.4-4.2（平均1.9），孔隙结构以墨水瓶状和平板状为主。③煤中显微裂隙以C型和D型为主，B型较少，几乎不含A型裂隙。④区内煤的兰氏体积普遍较高，空气干燥基范围为14.32-21.79m3/t，平均达17.18m³/t。（3）根据18块煤样品压汞曲线特征，定量标定了进汞曲线的4个“转折端”，发现四个转折端分别对应反映了煤中不同尺度的孔裂隙（即：微小孔、中孔、大孔和裂隙）。引入分形几何理论方法，定量计算了各个孔隙阶段的煤的分形维数。分析表明，自相似理论印证了4类孔-裂隙的存在。通过研究实现了不同级别孔裂隙的分段定量表征，初步确立了应用压汞曲线定量评价煤储层有利开发类型的方法。（4）采用低场核磁共振和CT无损检测技术，精细定量表征了煤的孔-裂隙结构特征。采用低场核磁共振方法计算了煤的总孔隙度、有效（可动流体）孔隙度和渗透率。首次开展了变温条件下的低场核磁共振实验，结果表明煤的孔隙结构受温度的影响，同一煤样在不同温度下的核磁共振T₂谱形态发生变化；而且不同煤阶煤具有不同的变化特征。利用CT无损检测分析技术定量分析了煤的孔裂隙发育、矿物质分布，并计算了煤的面孔隙率和矿物质含量。（5）研究区中新生代含煤盆地以气煤—瘦煤为主，变质程度相对偏高，仍以寻找热成因煤层气为主，生物成因气为辅。对于热成因气来讲，由于研究区经历了多期断陷作用，煤层气后期逸散严重，因此煤层气有利区主要分布于煤层较厚、顶板具备有效封盖层且具备有效的构造或水力封堵的区域。（6）在上述研究的基础上，优选了构造分区、煤级、沉积相、煤层累积厚度、含气量、埋深和渗透率七个主要地质因素，采用多层次模糊数学评价理论，在地理信息系统平台下，对五个重点含煤盆地的的煤层气有利区进行了评价。结果表明，煤层气有利目标区主要包括鸡西盆地的鸡东拗陷南部和鹤岗盆地的南山、峻德地区。采用容积法计算了各个盆地内的煤层气资源量和资源丰度，为该区煤层气的后续勘探开发提供了有利依据。更多还原

【Abstract】 Sanjiang-Mulinghe coal-bearing zone is rich in coalbed methane （CBM） resource, and isone of the most prospective low-rank CBM development districts in China. However, it isdifficult to ascertain CBM enrichment and its geological controls due to complicated tectonicevolution, various depositional environments of the coal-bearing strata, multiple and thin coalseams in the zone. In this paper,4basins （Hegang, Jixi, Hulin and Boli） and1depression（Suibin） were studied on geological setting, depositional environment, coal reservoir propertyand CBM enrichment. They were also evaluated comprehensively for favorable CBMdevelopment district. Results are as follows.（1） The study area underwent multiple tectonic uplift and subsidence. At ChengziheFormation stage, Boli and Jixi basins and Suibin depression underwent intensely tectonicsubsidence leading to the deposition of thick coal-bearing sedimentary system. In Hulin basin,thick coal-bearing strata were formed resulting from the Paleogene taphrogeny. At ChengziheFormation stage, the depositional environment is dominated by lacustrine facies in Suibindepression. Favorable coal-accumulation zone is located at delta front and shore-shallow lakeenvironment. Coal-accumulated environment is mainly composed of fluvial facies andfluvial-dominated delta in Boli basin, while delta plain and fluvial alluvial plain in Jixi basin.For Hulin basin, Paleogene Hulin Formation is the main coal-bearing strata, and itsdepositional environments are dominated by fluvial facies and lacustrine facies.（2） Many methods （mercury porosimetry, low-temperature N2, nuclear magneticresonance, X-CT, isothermal adsorption, proximate and ultimate analyses, etc.） were used forinvestigating coal reservoir physical properties. Results show that:（a） Coal macerals arecomposed of abundant vitrinite （34.0-95.1%）, moderate inertinite （0.6-62.7%） and a few ofexinite （0.7-18.2%）;（b） Coal pores are mainly dominated by micropore （mean55.9%）,secondly by mesopore and macrpore （mean22.3%and21.8%）. Volume content is higher forthe micropores （<10nm, in diameter） than that for the micropores with a diameter of10-100nm. Additionally, structural morphology of micropores is usually like ink-bottle andparallel-plate;（c） Types C and D are main microfractures in coals, while Type A is notexistent in coals;（d） Langmuir volume is relatively high in the zone ranging from14.32to21.79m3/t （mean17.18m3/t, in air-drying basis）.（3） Based on mercury porosimetry analyses of18coal samples, micro-, meso-,macropores and fractures were distinguished by the4“turning points” of mercury intrusioncurves. The method was verified by the fractal geometry theory used for calculating fractal dimensions of differently sized pore-fractures. Thus, the pore-fractures of coals werecharacterizated quantitively by mercury intrusion curves. Furthermore, concerning CBMexploitation, a new method evaluating favorable coal reservoirs was established by usingmercury porosimetry based on achievements above.（4） The pore-fractures of coals were studied by low-field nuclear magnetic resonance（NMR） and CT techniques in this paper. The porosity, effective porosity （mobile fluid） andpermeability of coals were evaluated by using NMR technique. T₂spectral distribution ofcoal will change resulting from the change of pore structure with increasing temperature. Thechange is different for coals with different rank. Coal pore-fractures and mineral matterdistribution can be quantitively analyzed by CT technique. Based on that, planar porosity andmineral matter content of coals were evaluated.（5） In the study area, the Mesozoic-Cenozoic coals are characterized by gas-lean coalswith relatively high metamorphic grade. Coalbed methane is mainly thermogenic, secondlybiogenic. However, thermogenic methane scattered and escaped seriously during multipletaphrogeny in the study area. Thus, favorable CBM development districts are alwayscharacterized by thick coalbed, good sealing-capping of roof and effective tectonic orhydrodynamic sealing.（6） Based on above-mentioned achievements, geological structure, coal rank, sedimentaryfacies, accumulated coal thickness, gas content, burial depth and permeability were selectedfor evaluating favorable CBM development districts by combining fuzzy mathematic theorywith GIS software on five primary coal-bearing basins. Results show that favorable districtsprimarily locate at southern Jidong depression, and Nanshan and Junde mines in Hegangbasin. Additionally, CBM resource and its abundance were calculated using volumetricmethod, which providing the foundation of the exploration and development of CBM.更多还原